CN113130983B - Solid electrolyte and solid lithium ion battery - Google Patents

Abstract

In order to overcome the problem of lithium dendrites existing in the existing solid electrolyte, the invention provides a solid electrolyte which is characterized by comprising a polymer and an additive, wherein the additive comprises a compound shown in the following structural formula 1:

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each independently selected from hydrogen, fluorine or a group containing 1 to 5 carbon atoms. Meanwhile, the invention also discloses a solid lithium ion battery comprising the solid electrolyte. The solid electrolyte provided by the invention can inhibit the growth of lithium dendrites in the charging and discharging processes, and improves the cycle performance.

Description

A kind of solid electrolyte and solid lithium ion battery

technical field

The invention belongs to the technical field of secondary batteries, and in particular relates to a solid electrolyte and a solid lithium ion battery.

Background technique

Compared with traditional electrochemical energy devices such as lead-acid and nickel-chromium batteries, lithium-ion batteries have become the most widely used commercial storage devices due to their advantages such as high energy density, high working voltage, no memory effect, long cycle life and environmental friendliness. energy system. Although traditional liquid lithium-ion batteries have good ionic conductivity and wettability, they also have safety problems such as poor thermal stability, flammability, and easy leakage. The current lithium-ion battery system with graphite as the negative electrode has been mass-produced and optimized for many years, and the energy density has hardly exceeded 300Wh/kg, which is difficult to meet the market's requirements for high cruising range. Therefore, lithium metal anode batteries with high theoretical energy density, such as Li-S and Li-O ₂ systems, etc., high-nickel, high-voltage ternary cathode materials equipped with silicon and silicon-carbon anode lithium-ion batteries have come into view. However, on the one hand, the traditional organic liquid electrolyte is easy to decompose on the surface of lithium metal, resulting in shortened battery life; at the same time, the liquid electrolyte cannot effectively inhibit the growth of lithium dendrites, which in turn leads to short circuit of the battery, thermal runaway and even fire. And the problem of explosion, on the other hand, the volume expansion of electrode materials in use all pose challenges to the design of batteries.

Solid-state electrolytes with higher energy density and excellent safety performance become the potential best way to replace liquid electrolytes to solve the above-mentioned problems. Polymer solid-state batteries have good interface contact with electrode materials and are compatible with existing lithium-ion battery production equipment. They are the most likely solid-state battery systems for large-scale applications. However, polymer electrolytes use relatively flexible organic substances, and the interfacial contact between electrodes and electrolytes in lithium batteries is relatively good, but there is a problem of low ionic conductivity, which cannot suppress lithium dendrites. When the metal lithium negative electrode is defective or uneven or the interface contact is not good during the preparation process, it will cause the generation of lithium dendrites, resulting in attenuation and failure of battery cycle performance, and at the same time, the yield of good products will decrease.

Therefore, there is an urgent need to develop a polymer solid electrolyte that can tolerate the defects of lithium metal and improve the yield and life of the battery.

Contents of the invention

Aiming at the problem that lithium dendrite growth in the existing solid electrolyte leads to attenuation and failure of battery cycle performance, the invention provides a solid electrolyte and a solid lithium ion battery.

The technical solution adopted by the present invention to solve the problems of the technologies described above is as follows:

In one aspect, the present invention provides a solid electrolyte, including a polymer and an additive, and the additive includes a compound represented by the following structural formula 1:

Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are each independently selected from hydrogen, fluorine, or groups containing 1-5 carbon atoms.

Optionally, the additive is dispersed on the surface and inside of the solid electrolyte.

Optionally, the group containing 1-5 carbon atoms is selected from hydrocarbon group, fluorinated hydrocarbon group, oxygen-containing hydrocarbon group, silicon-containing hydrocarbon group or cyano-substituted hydrocarbon group.

Optionally, each of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ is independently selected from hydrogen, fluorine, methyl, ethyl, trimethylsilyloxy, cyano or trifluoromethyl .

Optionally, the compound shown in structural formula 1 is selected from one or more of the compounds shown below:

Optionally, based on 100% of the total mass of the solid electrolyte, the mass percentage of the compound represented by the structural formula 1 is 0.01-20%.

Optionally, based on 100% of the total mass of the solid electrolyte, the mass percentage of the compound represented by the structural formula 1 is 0.01-10%.

Optionally, the polymer is a polar polymer, and the polymer includes alkylene oxide monomers, siloxane monomers, olefin monomers, acrylate monomers, and carboxylate monomers , polymers obtained by polymerization of at least one of carbonate monomers, amide monomers, and nitrile monomers, and their halogenated products;

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the polymer is 10-90%.

Optionally, the solid electrolyte also includes lithium salts, including LiBr, LiI, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiSCN, LiB ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiBF ₂ C ₂ O ₄ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ F) ₂ , LiN(SO ₂ F)(SO ₂ CF ₃ ), LiC(SO ₂ CF ₃ ) One or more of ₃ , LiPF ₂ (C ₂ O ₄ );

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the lithium salt is 10-80%.

Optionally, the solid electrolyte also includes inorganic fillers, the inorganic fillers include LiF, LiCl, Li ₂ CO ₃ , SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, Li ₇ La ₃ Zr ₂ O ₁₂ , Li _x La ₃ Zry A _{2-y O 12} , sulfide, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ , Li _2.88 PO _3.73 N _0.14 , One or more of montmorillonite, kaolin and diatomite, wherein A is one of Ta, Al and Nb, 6≤x≤7, 0.5≤y≤2;

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the inorganic filler is 0-40%.

Optionally, the solid electrolyte also includes a solvent, and the solvent includes one or more of carbonates, carboxylates, and fluorinated solvents;

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the solvent is 0-10%.

In another aspect, the present invention provides a solid lithium ion battery, comprising a positive electrode, a negative electrode, and the solid electrolyte as described above, and the solid electrolyte is located between the positive electrode and the negative electrode.

Optionally, the negative electrode includes a negative electrode active material, and the negative electrode active material includes lithium titanate, carbon material, Li _X Fe ₂ O ₃ , Li _y WO ₂ , lithium metal, lithium alloy, silicon-based alloy, tin-based alloy , one or more of metal oxides, conductive polymers, and Li-Co-Ni-based materials, wherein 0≤x≤1, 0≤y≤1.

Optionally, the negative electrode active material is lithium metal.

According to the solid electrolyte provided by the present invention, the compound shown in structural formula 1 is added to the polymer, and the compound can be uniformly dispersed and compounded and fixed in the polymer. Unlike traditional liquid electrolytes, when the battery is formed, it is only located at the interface of the solid electrolyte The compound represented by the structural formula 1 can react with the negative electrode to form a uniform interface layer on the surface of the negative electrode. The interface layer has the characteristics of conducting lithium ions, so that the migration rate of lithium ions at the interface tends to be uniform, reducing the migration rate. Gradient, which is conducive to the uniform intercalation/deposition of lithium, while the compound shown by structural formula 1 inside the solid electrolyte is in an unreacted state. At the same time, the interface layer formed by the reaction between the compound represented by the structural formula 1 and the negative electrode has a certain mechanical strength, which can inhibit the formation of lithium dendrites. On the other hand, if the compound shown in structural formula 1 inside the solid electrolyte generates lithium dendrites during the charging and discharging process of the battery, when the lithium dendrites enter the solid electrolyte, they will interact with the compound shown in structural formula 1 inside the solid electrolyte. The compound reaction further forms a passivation film with high mechanical strength, which exerts resistance to the lithium dendrite sites, thereby further inhibiting the growth of lithium dendrites and improving the cycle performance of solid-state lithium-ion batteries.

detailed description

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

An embodiment of the present invention provides a solid electrolyte, including a polymer and an additive, and the additive includes a compound represented by the following structural formula 1:

Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are each independently selected from hydrogen, fluorine, or groups containing 1-5 carbon atoms.

A compound represented by structural formula 1 is added to the polymer, which can be uniformly dispersed and compounded in the polymer. Unlike traditional liquid electrolytes, only the compound represented by structural formula 1 located at the solid electrolyte interface can It reacts with the negative electrode to form a uniform interface layer on the surface of the negative electrode. The interface layer has the characteristics of conducting lithium ions, so that the migration rate of lithium ions at the interface tends to be uniform, reducing the migration rate gradient and facilitating the uniform intercalation/intercalation of lithium ions. deposition, while the compound represented by structural formula 1 inside the solid electrolyte is in an unreacted state. At the same time, the interface layer formed by the reaction between the compound represented by the structural formula 1 and the negative electrode has a certain mechanical strength, which can inhibit the formation of lithium dendrites. On the other hand, if the compound shown in structural formula 1 inside the solid electrolyte generates lithium dendrites during the charging and discharging process of the battery, when the lithium dendrites enter the solid electrolyte, they will interact with the compound shown in structural formula 1 inside the solid electrolyte. The compound reaction further forms a passivation film with high mechanical strength, which exerts resistance to the lithium dendrite sites, thereby further inhibiting the growth of lithium dendrites and improving the cycle performance of solid-state lithium-ion batteries.

In some embodiments, the additive is dispersed on the surface and inside of the solid electrolyte.

In some embodiments, the group containing 1-5 carbon atoms is selected from hydrocarbyl, fluorohydrocarbyl, oxygen-containing hydrocarbyl, silicon-containing hydrocarbyl or cyano-substituted hydrocarbyl.

In some embodiments, each of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ is independently selected from hydrogen, fluorine, methyl, ethyl, trimethylsilyloxy, cyano, or trifluoro methyl.

In some embodiments, the compound represented by the structural formula 1 is selected from one or more of the compounds shown below:

It should be noted that the above are some of the compounds claimed in the present invention, but are not limited thereto, and should not be construed as limiting the present invention.

In some embodiments, based on 100% of the total mass of the solid electrolyte, the mass percentage of the compound represented by the structural formula 1 is 0.01-20%.

In a preferred embodiment, based on 100% of the total mass of the solid electrolyte, the mass percentage of the compound represented by the structural formula 1 is 0.01-10%.

In a more preferred embodiment, based on 100% of the total mass of the solid electrolyte, the mass percentage of the compound represented by the structural formula 1 is 0.05-10%.

If the content of the compound shown in the structural formula 1 is too small, it is not enough to react with the lithium dendrites produced in the electrochemical process of the solid-state lithium-ion battery, and the effect of inhibiting the lithium dendrites is poor, and it is difficult to improve the performance of the solid-state lithium-ion battery. Performance; if the content of the compound shown in the structural formula 1 is too much, the deposition thickness of the interfacial layer formed by the reaction between the compound at the interface of the solid electrolyte and the negative electrode is too large, and the lithium ion conductivity of the excessively thick interfacial layer is reduced, and lithium ions in the The migration resistance of the interface layer increases, and the polarization of the solid-state lithium-ion battery is serious during the charging and discharging process, which is not conducive to the improvement of the cycle stability of the solid-state lithium-ion battery, and the internal resistance of the battery increases, and the initial capacity decreases.

In some embodiments, the polymer is a polar polymer.

The polar groups on the polymer chain dissolve and dissociate the lithium salt through Lewis acid-base action, and lithium ions are transported through the movement of the polymer chain.

In some embodiments, the polymer includes alkylene oxide monomers, siloxane monomers, olefin monomers, acrylate monomers, carboxylate monomers, carbonate monomers, amides Polymers obtained by polymerization of at least one of quasi-monomers and nitrile monomers and their halides;

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the polymer is 10-90%.

In some embodiments, the solid electrolyte further includes a lithium salt, and the lithium salt includes LiBr, LiI, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiSCN, LiB ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiBF ₂ C ₂ O ₄ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ F) ₂ , LiN(SO ₂ F)(SO ₂ CF ₃ ), LiC(SO One or more of ₂ CF ₃ ) ₃ , LiPF ₂ (C ₂ O ₄ ).

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the lithium salt is 10-80%.

In some embodiments, the solid electrolyte further includes inorganic fillers, the inorganic fillers include LiF, LiCl, Li ₂ CO ₃ , SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, Li ₇ La ₃ Zr ₂ O ₁₂ , Li _x La ₃ Zry A _{2-y O 12} , sulfide, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ , Li _2.88 PO _3.73 N _0.14 . One or more of montmorillonite, kaolin and diatomite, wherein A is one of Ta, Al and Nb, 6≤x≤7, 0.5≤y≤2;

By adding inorganic fillers to the solid electrolyte, the mechanical properties of the solid electrolyte can be further improved, and the growth of lithium dendrites can be suppressed. At the same time, the inorganic filler can reduce the crystallinity of the polymer, improve the mobility of the polymer chain segment, thereby increasing the migration speed of lithium ions in the polymer, bringing higher ionic conductivity to the solid electrolyte, and helping to reduce the electrical conductivity. Polarization in chemical processes.

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the inorganic filler is 0-40%.

When the weight content of the inorganic filler is too high, the mechanical strength of the solid electrolyte is affected, and the film-forming property becomes poor.

The median particle diameter D50 of the inorganic filler is 5 nm˜5 μm.

In some embodiments, the solid electrolyte further includes a porous framework on which the polymer is supported.

In some embodiments, the porous framework is selected from bacterial cellulose membranes.

In some embodiments, the solid electrolyte also includes a solvent, and the solvent includes one or more of carbonates, carboxylates, and fluorinated solvents;

Based on the total mass of the solid electrolyte as 100%, the mass percentage of the solvent is 0-10%.

In another aspect, the present invention provides a solid lithium ion battery, comprising a positive electrode, a negative electrode, and the solid electrolyte as described above, and the solid electrolyte is located between the positive electrode and the negative electrode.

In some embodiments, the positive electrode includes a positive electrode active material, and the positive electrode active material includes _LiNix Co _{y Mnz} L _(1-xyz) O ₂ , LiCo _x' L _{(1-x') O 2} , LiNix _" At least one of L'_y' Mn _(2-x"-y') O ₄ , Li _z' MPO ₄ ; wherein, L is Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe ;0≤x≤1, 0≤y≤1, 0≤z≤1, 0<x+y+z≤1, 0<x'≤1, 0.3≤x"≤0.6, 0.01≤y'≤0.2;L' is Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe; 0.5≤z'≤1, and M is at least one of Fe, Mn and Co.

Specifically, the positive electrode active material is selected from one or more of lithium cobalt oxide, nickel cobalt aluminum, nickel cobalt manganese, lithium iron manganese phosphate, lithium manganate, and lithium iron phosphate.

In some embodiments, the positive electrode further includes a positive electrode binder and a positive electrode conductive agent.

In some embodiments, the negative electrode includes a negative electrode active material, and the negative electrode active material includes lithium titanate (LTO), carbon material, Li _X Fe ₂ O ₃ , Li _y WO ₂ , lithium metal, lithium alloy, silicon-based One or more of alloys, tin-based alloys, metal oxides, conductive polymers, and Li-Co-Ni-based materials, where 0≤x≤1, 0≤y≤1.

In some preferred embodiments, the negative electrode active material is lithium metal.

The carbon material includes non-graphitizable carbon and graphitizable carbon.

The metal oxides include SnO, SnO ₂ , PbO, Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ One or more of O ₄ , Bi ₂ O ₅ and titanium oxide

The conductive polymer includes polyacetylene.

In some embodiments, the negative electrode further includes a negative electrode binder and a negative electrode conductive agent.

The solid-state lithium-ion battery has good cycle stability due to the use of the above-mentioned solid-state electrolyte, and can effectively avoid battery short-circuit and increase in polarization voltage caused by lithium dendrites.

The present invention is further described by way of examples below.

Example 1

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including the following steps:

Preparation of polymer solid electrolyte:

The additive used is Compound 1. Dissolve 1.0g of polyethylene oxide (PEO) with a weight average molecular weight of 60W and 0.41g of LiN(SO ₂ CF ₃ ) ₂ in 5g of acetonitrile, then add 0.029g of Compound 1, and stir until solid completely dissolved. The obtained polymer solution was placed on a coating machine, automatically scraped with a scraper, dried in vacuum at room temperature for 8 hours, and then dried in vacuum at 80°C for 12 hours to obtain a polymer solid electrolyte with a thickness of 40 μm. The content of Compound 1 in the electrolyte accounts for 2% of the total weight of the electrolyte.

Preparation of solid-state lithium-ion batteries:

Positive electrode: Mix LiFePO ₄ active material, conductive carbon black, and the above-mentioned polymer electrolyte in a mass ratio of 80:10:10, add cyclohexanone, and stir until the mixture is uniform. The slurry obtained above was evenly coated on an aluminum foil, firstly dried at 80°C until there was no obvious liquid, and then dried under vacuum at 100°C for 12 hours.

Negative electrode: Lithium metal is used as the negative electrode.

Preparation of solid-state lithium-ion battery: Assemble 2032 button batteries in the order of negative electrode case-shrapnel-gasket-negative electrode-polymer solid electrolyte-positive electrode-positive electrode case.

Example 2

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

Polypropylene carbonate (PPC) was used instead of polyethylene oxide (PEO) in Example 1.

Example 3

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

The lithium salt LiN(SO ₂ CF ₃ ) ₂ in Example 1 was replaced by LiCF ₃ SO ₃ .

Example 4

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

In the "preparation of polymer solid electrolyte" operation, add 0.1656g of nano-alumina to the polymer solution, the size of nano-alumina is 8-12nm, d50=10nm, and perform ultrasonic dispersion. After ultrasonic dispersion, the solid electrolyte solution Place in a polytetrafluoroethylene template to dry, volatilize at room temperature for 4 hours, and then dry in vacuum at 60°C for 6 hours to obtain a solid polymer electrolyte.

Example 5

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

In the "preparation of polymer solid electrolyte" operation, after the configuration of the solid electrolyte solution is completed, the bacterial cellulose membrane is obtained. The porosity of the bacterial cellulose membrane is calculated as 85vol% by the Archimedes method, and the solid electrolyte solution infiltrates Put it into the bacterial cellulose membrane, volatilize the solvent at room temperature and then infiltrate the solid electrolyte solution. Repeat the operation until the pores are completely filled with the polymer, and then vacuum dry at 60°C for 6 hours to obtain a solid electrolyte. The average thickness of the solid electrolyte membrane is 52 μm.

Example 6

This embodiment is used to illustrate the preparation method of the solid-state electrolyte and solid-state lithium-ion battery disclosed in the present invention, including most of the operation steps in Example 3, the difference being:

The positive electrode active material LiFePO ₄ in Example 1 was replaced by LiFe _0.5 Mn _0.5 PO ₄ .

Example 7

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

的化合物3替换实施例1中的化合物1。The structural formula is

Compound 3 replaces Compound 1 in Example 1.

Example 8

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

的化合物4替换实施例1中的化合物1。The structural formula is

Compound 4 replaces Compound 1 in Example 1.

Example 9

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

的化合物8替换实施例1中的化合物1。The structural formula is

Compound 8 replaces Compound 1 in Example 1.

Example 10

This embodiment is used to illustrate the preparation method of the solid electrolyte and solid lithium ion battery disclosed in the present invention, including most of the operation steps in Example 1, the difference is:

的化合物9替换实施例1中的添加剂。The structural formula is

Compound 9 replaces the additive in Example 1.

Comparative example 1

This comparative example is used to compare and illustrate the preparation method of the solid-state electrolyte and solid-state lithium-ion battery disclosed by the present invention, including most of the operating steps in Example 1, the difference being:

In the operation of "preparation of polymer solid electrolyte", no compound represented by structural formula 1 is added to the polymer solution.

Comparative example 2

This comparative example is used to compare and illustrate the preparation method of the solid-state electrolyte and solid-state lithium-ion battery disclosed by the present invention, including most of the operating steps in Example 6, the difference being:

In the operation of "preparation of polymer solid electrolyte", no compound represented by structural formula 1 is added to the polymer solution.

Performance Testing

The following performance tests were carried out on the solid-state electrolytes and solid-state lithium-ion batteries prepared in the above-mentioned Examples 1-10 and Comparative Examples 1 and 2:

The solid-state lithium-ion batteries prepared in Examples 1-10 and Comparative Examples 1 and 2 above were subjected to a charge-discharge cycle test on a blue battery tester, and the test temperature was 60°C. The solid-state lithium-ion batteries of Examples 1-5, 7-10 and Comparative Example 1 are charged to 3.8V with a current of 0.2C, then charged at a constant voltage until the current drops to 0.20mA, and then discharged at a constant current of 0.2C to 3.8V. 2.8V, cycle 200 cycles; the solid-state lithium-ion battery of Example 6 and Comparative Example 2 was charged to 4.2V with a current of 0.2C, then charged at a constant voltage until the current dropped to 0.20mA, and then discharged to 3.0V with a current of 0.2C , cycled for 200 cycles, and calculated the capacity retention rate of the battery according to the formula "capacity retention rate = discharge capacity of the 300th cycle/discharge capacity of the first cycle × 100%". According to the formula "Coulombic efficiency = discharge capacity per week/charge capacity per week × 100%", calculate the first-cycle coulombic efficiency of the battery, and the average coulombic efficiency of N cycles = the sum of N-week coulombic efficiencies/N,

The obtained test results are filled in Table 1.

Table 1

Comparing the test results of Comparative Example 1 and Example 1 in Table 1, it can be seen that when 2wt% of Compound 1 is added to the solid electrolyte as an additive, although the first-week Coulombic efficiency of Example 1 is lower than that of Comparative Example 1, its cycle The average Coulombic efficiency is much higher than that of Comparative Example 1, mainly because the additive participated in the electrochemical reaction on the surface of the negative electrode in the first week, forming a new interfacial layer on the surface of lithium metal. In Comparative Example 1, a short circuit occurred at 120 cycles, which was caused by metal lithium dendrite growth piercing the electrolyte, while in Example 1, the capacity retention rate was above 80% after 480 cycles. The data of Example 6 and Comparative Example 2 also verified the above conclusions.

Comparing the battery performance results of Examples 1 to 10, it can be seen that the battery prepared by using the solid polymer electrolyte of the present invention has an average coulombic efficiency of more than 98.2% at 0.2C cycle at 60 ° C, and LiFePO is used as the positive electrode _. The capacity retention rate of the battery at 0.2C cycle is above 80%, and the cycle cycle is above 456 cycles, indicating that the addition of additives plays an important role in inhibiting the formation of lithium dendrites and prolonging the life of solid-state lithium-ion batteries. As can be seen from the test results of Example 6 and Comparative Example 2, when using different positive electrode materials such as LiFe _0.5 Mn _0.5 PO ₄ as the positive electrode material, the cycle performance of the solid-state lithium-ion battery is also significantly improved, indicating that the solid-state lithium ion battery provided by the present invention The electrolyte is suitable for different cathode material systems. Comparing Example 1 and Example 5, it can be found that when the porous framework is introduced into the electrolyte, the number of cycle cycles with a battery cycle capacity retention rate of more than 80% is improved. This is because the introduction of the porous framework improves the mechanical strength of the electrolyte and reduces the The glass transition problem of the electrolyte can more effectively inhibit the dendrite growth of the negative electrode.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (10)

1. A solid state electrolyte comprising a polymer and an additive, the additive comprising a compound represented by the following structural formula 1:

structural formula 1

Wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each independently selected from hydrogen, fluorine or a group containing 1 to 5 carbon atoms;

the mass percentage of the compound shown in the structural formula 1 is 0.01-2% based on 100% of the total mass of the solid electrolyte.

2. The solid electrolyte of claim 1, wherein the additive is dispersed on the surface and in the interior of the solid electrolyte.

3. The solid electrolyte according to claim 1, wherein the group having 1 to 5 carbon atoms is selected from a hydrocarbon group, a fluorinated hydrocarbon group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, or a cyano-containing substituted hydrocarbon group.

4. The solid state electrolyte of claim 1, wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each independently selected from hydrogen, fluoro, methyl, ethyl, trimethylsiloxy, cyano or trifluoromethyl.

5. The solid electrolyte of claim 1, wherein the compound of formula 1 is selected from one or more of the following compounds:

compound 1 Compound 2

Compound 3 Compound 4

Compound 5 Compound 6

Compound 7 Compound 8

Compound 9.

6. The solid electrolyte according to claim 1, wherein the polymer is a polar polymer, and the polymer comprises a polymer obtained by polymerizing at least one of alkylene oxide monomers, siloxane monomers, olefin monomers, acrylate monomers, carboxylate monomers, carbonate monomers, amide monomers, nitrile monomers, and a halide thereof;

the mass percentage of the polymer is 10-90% based on the total mass of the solid electrolyte being 100%.

7. The solid state electrolyte of claim 6, further comprising a solvent comprising one or more of a carbonate, a carboxylate, a fluorinated solvent;

the mass percentage of the solvent is 0-10% based on 100% of the total mass of the solid electrolyte.

8. A solid-state lithium ion battery, characterized by comprising a positive electrode, a negative electrode and the solid-state electrolyte according to any one of claims 1 to 7, wherein the solid-state electrolyte is positioned between the positive electrode and the negative electrode.

9. The solid state lithium ion battery of claim 8, wherein the negative electrode comprises a negative active material comprising lithium titanate, carbon materials, li _X Fe ₂ O ₃ 、Li _y WO ₂ One or more of lithium metal, lithium alloy, silicon alloy, tin alloy, metal oxide, conductive polymer and Li-Co-Ni-based material, wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.

10. The solid state lithium ion battery of claim 9, wherein the negative active material is lithium metal.